Abrasion-resistant materials and certain alloys therefore

ABSTRACT

A novel group of alloys consisting essentially of: A. columbium and/or tantalum and/or vanadium; B. titanium and/or zirconium; C. chromium and/or manganese and/or rhenium; and optionally, D. molybdenum and/or tungsten Such alloys illustrate utility in themselves and when nitrided as hereinafter taught are characterized by excellent wear and abrasion resistance and show considerable utility, for example, as cutting tool materials.

United States Patent Rausch et al.

[ 1 Feb. 22, 1972 ABRASION-RESISTANT MATERIALS AND CERTAIN ALLOYS THEREFORE Assignee:

Filed:

Appl. No.: 6,379

Inventors: John J. Rausch, Antioch; Ray .1. Van

Thyne, Oak Lawn, both of 111.

Surface Technology Corporation, Stone Park, 111.

Jan. 28, 1970 US. Cl ..148/3l.5, 29/182.5, 75/134,

Int. Cl ..C22c 27/00, C230 1 1/14 FieldofSe-arch ..l48/13.1, 16.6, 203,315, 148/34, 39, 32, 133; 75/134, 174, 205, 208, 224;

References Cited UNITED STATES PATENTS 9/1935 Austin ..148/20.3 5/1937 Kelly ..75/174 X 8/1939 Van Note ..148/20.3 8/1957 Wyatt et a1 ..148/l33 X optionally, V w.

I YA IIAYAAVAY Wlodek et a1 .1: ..75/n4 OTHER PUBLICATIONS llT Research Institute. 1R Reports lR-7187(l) and (11) Aug. 22, 1967 and Sept. 7, 1967 7 Primary ExaminerCharles N. Lovell Attorney-Albert Siege] [57] ABSTRACT A novel group of alloys eonsisting essentially of:

A. columbium and/or tantalum and/or vanadium;

B. titanium and/or zirconium;

C. chromium and/or manganese and/or rhenium; and

D. molybdenum and/or tungsten 12 Claims, 1 Drawing Figure ABRASION-RESISTANT MATERIALS AND CERTAIN ALLOYS THEREFORE BACKGROUND OF THE INVENTION This invention relates to a novel group of ternary or higher alloyed metals which alloys contain essentially:

a. one or more metals of the group columbium, tantalum and vanadium;

b. one or more metals of the group titanium and zirconium;

c. one or more metals of the group chromium, manganese and rhenium; and

d. as optional alloying materials in the aforesaid ternary or more complex systems one or both metals of the group molybdenum and tungsten,

in amounts of percent by weight as hereinafter set forth. We have discovered that such alloys, particularly when nitrided as herein taught, form extremely useful high-speed cutting materials (although they hayeother uses also) and offer considerable advantages in terms of cutter life, performance and cost over presently known cutting tool materials, especially sintered carbides. In addition such materials have excellent wear and abrasion resistant characteristics, all of which is hereinafter described. The commercial and technical significance of our invention should be immediately apparent to those skilled in this particular art.

A principal object of our invention is to provide novel nitrided alloys as aforesaid.

Another object of our invention is to provide a novel group of materials characterized by excellent wear and abrasion resistance and cutting tool properties consisting of an alloy composite having a nitrided zone extending from the surface inwardly.

Still another object of our invention is to provide a number of novel alloys from within this group. These and other objects, features and and advantages of our invention will become apparent to those skilled in this particular art from the following detailed disclosure thereof, and from the accompanying drawing.

DESCRIPTION OF THE PRIOR ART AND FURTHER BACKGROUND COMMENTS To the best of our knowledge the products or our invention which are fully set forth as this description proceeds are nowhere described in the prior art. We find nothing in the art which in any way indicates the present alloys or the nitrided composite materials of the present disclosure. In fact, there are certain teachings in the art which would indicate that the nitrided alloys of our invention would be too brittle to be useful and accordingly it is with some surprise that the utility of such materials is as we have discovered.

For example, it is known in the art that the nitriding at elevated temperatures of elemental tantalum, columbium or titanium or dilute titanium alloys generally results in the formation of continuous, hard nitrided surfaces layer thereof and such layers are usually characterized as being brittle. In distinction to such prior art teachings we have found that we can make an exceptionally useful group of materials which result from the reaction of the present alloy compositions with a nitrogen environment. Upon being nitrided the present materials are characterized by a desirable combination of mechanical properties which make them extremely useful under severe conditions of erosion or abrasion.

SUMMARY OF THE INVENTION When nitrided as herein taught the present materials are characterized by a gradated, multiphase structure lessening in nitride content from the surface inwardly.

We have found that truly effective nitrided composites falling within the scope hereof may only be produced when certain combinations of metals and specific ranges are present in the alloys prior to nitriding. As noted above the present alloys prior to being nitrided must contain at least three metallic components, namely;

a. one or more of the metals columbium, tantalum, and vanadium;

b. one or more of the metals titanium and zirconium; and

c. one or more of the metals chromium, manganese and rhenium.

It also should be noted that certain amounts of molybdenum and/or tungsten may be incorporated herein as optional alloying ingredients.

BRIEF DESCRIPTION OF THE DRAWING In the drawing appended hereto FIGURE is a ternary diagram for nitrided alloys in the vanadium-titanium-chromium system.

EXPERIMENTAL PROCEDURES Before commencing a detailed discussion of our invention we wish to first describe the experimental procedures we employed and the criteria established whereby we determined the utility of the present materials particularly in the nitrided condition. All of this could be written as a series of examples (and should be considered as such) but for purposes of brevity we present the data in tabular form.

In our experimental work a series of alloys were melted under an inert atmosphere in a nonconsumable electrode arc furnace using a water-cooled, copper hearth. High purity materials (greater than 99.5 percent) were used for the alloy charges and generally weighed about 70 grams. These procedures are of course quite well known to those skilled in the art.

The alloys were cut into specimens approximately Va-inch thick and reacted in nitrogen at atmospheric pressure. The resulting structures, thickness and microhardnesses of the various reaction zone or layers were determined using standard metallographic techniques. A variety of tests were used to evaluate the strength and toughness of these materials for potential use in abrasive wear or metal cutting applications.

The metal cutting tests were performed using the nitrided materials as tool inserts %X% inch having a 0.030'inch nose radius which was used as a section of the cutting surface. Such radii were ground on the specimens prior to nitriding.

The alloy samples as thus prepared were subsequently nitrided. For nitriding we used a cold wall furnace embodying a molybdenum heating element and radiation shields with the furnace being evacuated to 5 microns pressure and flushed with nitrogen prior to heating. Temperatures were measured with an optical pyrometer, namely a Leeds and Northrop Optical Pyrometer, catalog number 862, sighting on an unnitrided molybdenum heating element which completely surrounded the specimens. The temperatures given herein are corrected from this source. We used a correction factor determined by using a tungsten-rhenium thermocouple in conjunction with the sightings of the aforesaid optical pyrometer.

Following nitrided sample preparation, lathe turning tests were run on A151 4340 steel having a hardness of Rockwell C (Re), 44. A feed rate of 0.005 inch per revolution and depth of cut of 0.050 inch were used. A standard negative rake tool holder was employed with a 5 back rake and a 15 side cutting edge angle. Tool wear was measured after removing a given amount of material.

Our principal criterion in determining whether the present nitrided materials passed or failed and thus whether they are useful or not for purposes of the present invention was the ability to remove 2 cubic inches of hardened steel at a speed of 750 SFM (surface feet per minute). Furthermore, we evaluated the toughness and chipping resistance by using diamond hardness indentation (standard Rockwell A scale 60 kg. load) and also by lathe cutting at SFM to remove 1 cubic inch of the steel which is a good measure of chipping resistance under load. All of our materials pass such tests.

It should be noted that for any ternary metallic system described herein the difference between what we claim as our nitrided materials and other compositions within the same system falling outside of the scope hereof is very substantial.

nun

In the experimental discussions set forth in this specification the following conditions apply unless otherwise specified:

i. all nitriding was carried out in molecular nitrogen at atmospheric pressure for 2 hours.

2. the specimens were of the size set forth above, namely, xii-inch thick.

DESCRIPTION OF THE INVENTION We have discovered a novel group of composite materials characterized by high surface hardness and useful wear resistance. Such materials are formed when alloys within our prescribed compositional ranges as hereinafter taught are reacted with nitrogen or an environment which is nitriding to the alloys at elevated temperatures. The resulting material is highly resistant to thermal and mechanical shock. Nitride formation lessens as one moves inward from the surface.

Most of the unreacted alloys included within the scope of our invention are generally single phase solid solutions over the range of temperatures employed for nitriding. As the nitriding reaction proceeds, the nitrogen diffuses inwardly and there is developed a multiphase structure, that is, a microstructure consisting of two or more phases, usually differing in nitrogen content as well as metallic content, which are discernable when observed in cross section under a microscope using typical metallographic techniques. We would note, to avoid any misunderstanding, that the term phase" as used herein means a physically homogeneous and distinct portion of a materials system and that multiphase" means two or more of such phases. Of course, some hardening can occur even below the metallographically observed reaction zone by the presence of nitrogen in solid solution.

The range of useful materials in the system vanadium-titanium-chromium, nitrided, is illustrated in the ternary phase diagram FIGURE. In such system we find that the vanadium content may range from 30 to 85 percent, the chromium content from 2 to 45 percent and the titanium content from 5 to 50 percent.

To obtain the desired nitrogen pickup we typically nitride such vanadium-titanium-chromium alloys at temperatures above 2,000 F. The three elemental metals, when treated alone form thick continuous nitrided layers upon exposure to nitrogen. We find that upon nitriding at 2,850 F. for 2 hours in molecular nitrogen, for example, layers on vanadium or titanium show serious chipping around Rockwell A impressions and both materials fail immediately at 750 SFM cutting tests. We have found that chromium is embrittled with nitrogen to the extent that after nitriding at 2,450 F. the specimens fracture when the Rockwell impression is made. (The foregoing Rockwell impressions are Rockwell A). Additionally, we have found that after nitriding a binary alloy of V- 60 Cr at 2,250" or 2,450 F. the outer nitrided layer is largely spilled off upon removal from the furnace and such material is not included within the scope of our invention.

We also find that relatively dilute alloys, that is titanium or vanadium or chromium rich alloys when nitrided are not useful. For example, V-5Ti-5Cr nitrided at 2,450 F., shows chipping around the Rockwell A impression and fails immediately by high wear when cutting at 750 SFM. When nitrided at 2,850 this alloy shatters when the cutting test is attempted and broke when the Rockwell A impression was initiated. V-l0Ti-75Cr is brittle after nitriding at 2,450 F. for 2 hours. An alloy of V-65Ti-10Cr nitrided over a wide range of temperatures showed chipping during the Rockwell A test and the material failed upon cutting at 750 SFM. Similarly nitrided V-40Ti-40r did not cut at 750 SFM and showed another defeet that was observed with the high titanium content materials, there was pronounced dimensional increase at the edges which leads to chipping of such raised edges. These materials are not included within the scope of our invention.

The problems using the compositions noted above were overcome in a wide range of nitrided ternary vanadiumchromium alloys defined in the FIG. Such alloy system is representative of the present materials. In such alloys little dimensional changes occur as the materials are nitrided; typically the volume change is less the 1 percent, the materials cut well at 750 SFM and the propensity for chipping is minimized. The materials of such system included within the scope of our invention fall within the compositional boundary of the polygon ABCDEFG of the FIG.

Such materials illustrate a fine dispersion of nitrided phases decreasing in content essentially from the surface inward. The difference in hardness grading between V-20 Ti-20 Cr, one of the ternary alloys included within the scope of our invention and V-65 Ti-lO Cr which failed and is not included within the scope of our invention is shown below:

TABLE 1 Distance from faces of metallographically polished cross sections using a 50 gram load at 0.5 mil and a 200 gram load at l to 8 mils from the surface. Although the hardness at the outer surface is similar in both nitrided alloys and in both examples is much higher than the hardness of commercial sintered carbide, the difference between the grading and therefore the support of the hard surface is evident. Our materials can cut at 750 SFM with lower tool wear than commercially available sintered carbide tool materials.

The useful materials can be nitrided over a range of temperatures and times. Data for V-25 Ti-lO Cr nitrided for 2 hours follow:

Nitriding Metallographically Nitrogen Temperature observed reaction Pickup Hardness (F.) zone (inches) (mg/Cm?) (Ra) scope of our invention and the nitrided alloys that fail are not included.

TABLE II Nitriding Treatment Cutting Composition Temperature Time Test (Weight (F.) (hr.) Results Unalloyed V 2850 2 F Unalloyed Ti 2850 2 F V-5Ti-5 Cr 2850 2 F V-S Ti-S Cr 2450 2 F V-S Ti-5 Cr 2250 4 F V-5 Ti-S Cr 2250 B(4+4) F V-l3 Tl-l3 Cr 2450 2 P v-20 Ti-20 Cr 2450 2 F v-20 r020 Cr 2250 4 F v-25 Ti4o Ct 2450 2 F v-ao Ti-2 c; 2550 2 F v-40 Ti 2550 2 F v-40 Ti 2650 2 F V-40 Ti 2450 2 F v-40 Ti 2250 4 F v-40 Ti 2250 8 4+4 F v-54 Ti-lS Cr 2250 4 F v-2s rt-25 Cr 2450 2 F v45 Ti-40 Cr 2450 2 F v45 Ti-40 Cr 2250 2 F v-05 Ti-lO Cr 2550 2 F was Ti-IO Cr 2050 2 F v-40 Ti-40 Cr 2450 2 F v40 Tms Cr 2450 2 F v40 CT 2250 4 F v-so Cr 2450 2 F v-eo Cr 2250 2 F Unalloyed Ct 2450 2 Brittle Unalloyed Cr 2250 2 Brittle v5 205 c; 2250 2 F v-5 2:5 Cr 2250 2 F v 5 2:5 Cr 2450 2 F v 20 Zr-2O Cr 2450 2 F v-30 2050 Cr 2450 2 F v-50 2:40 Cr 2450 2 F v.50 21-40 Cr 2450 4 (2+2) F was Zr 2250 2 F v 55 Zr 2250 2 F v45 2: 2450 2 F v-70 2:40 Cr 2450 2 F v40 Zr-IO Cr 2450 2 F v-10 2:40 Cr 2050 2 F V50 2040 Cr 2250 2 Brittle V50 2020 Cr 2450 2 Brittle Cb-S Ti-5 Cr 2850 2 F c045 Ti-l5 Cr 2050 2 F c045 Ti-lS Cr 2450 2 F -20 Ti40 Ct 2050 2 F 00-30 Ti-lO Cr 2450 2 F Cit-65 Ti-lO Cr 2550 4 F c055 Ti-IO Cr 2550 2 F Cb-65 Ti-IO Cr 2550 0 2+4 F 00-30 Zr-lO Cr 2450 4 F Cb-35 Zr'S Cr 2450 4 P Ta-20 Ti-l0 Cr 2850 2 F Ta-30 2:40 Cr 2450 4 F v-25 Ti45 M040 Cr 2450 2 F 00 25 Ti-IO M0-5 Cr 2550 2 F c020 Ti-l5 M040 Cr 2850 2 F c020 Ti-lS M040 Cr 2650 2 P Ta-ZO Ti-IO M040 Cr 2550 4 P Ta-20 Ti-lO W-IO Cr 2550 2 F v-25 Ti40 Re 2450 2 F v 25 Ti-lO Re 2250 4 F Cb-ZS Ti-ZO Re 3250 2 F Cb-30 Ti Re 3250 2 P Cb-IS Ti-40 R0 2250 2 F c040 Ti-lO Re 5250 2 F Ta-ZS Ti-l5 Re 3250 2 F 00-30 Zr-20 Re 5250 2 F ClJ-25 Ti-lO M040 R0 5250 2 F v-25 Ti-IO Mn 2250 8 4+4 F c040 Ti40 Mn 5250 2 F v-25 Ti-IO Mo-Mn 2450 2 F 00.25 Ti-lO M040 Mn 5050 2 F P Pass-removes 2 cu. in. of 4340 steel workpiece at 750 SFM with tool wearland less than 0.040 inches and also removes at least 1 cu. in. at [00 SFM.

F Fails at 750 SFM Another alloy system representative hereof are nitrided alloys of the composition vanadium-zirconium-chromium. In such system the vanadium ranges from 30 to 85 percent, the zirconium from 5 to 50 percent and chromium from 2 to 45 percent. Such alloys differ somewhat from the titanium containing ternary alloys previously described in that the microstructure is different. Here the structure of the alloys prior to nitriding is multiphase and the nitriding reaction is somewhat more complex than in the case of vanadium-titaniumchromiurn where the alloys per se are single phase. However, the same principles of complex alloying to achieve the desired relative reactivity and grading are observed with the V-Zr-Cr alloys. During nitriding, the inwardly diffusing nitrogen partitions between the initial two phases and may form new phases. A grading inwardly of microstructure and nitrogen content is again observed. As shown in Table II, the same alloying principles apply as was shown above, nitrided vanadium rich or zirconium rich compositions such as V-5 Zr-5 Cr or V-7O Zr- 1 0 Cr, respectively, fail in cutting at 750 SFM and are not included within the scope of our invention also shows evidence of melting at these desired nitriding temperatures. However, a range of nitrided alloys having excellent performance has been shown for such alloyed compositions as V-20 Zr-20 Cr. V-30 Zr-30 Cr, and V-30 Zr-lO Cr, and these are included within the scope of our invention.

A number of examples of nitrided Cb-Ti-Cr compositions are given in Table II. The improved wear resistance achieved by nitriding at more elevated temperatures was demonstrated with Cb-15Ti-l5 Cr which is included within the scope of our invention. The tool wear after our standard 750 SFM test was 0.013 in and 0.005 in after nitriding at 2,450 F. and 2,650 F., respectively.

Other examples of useful nitrided compositions of Cb-Zr- Cr, Ta-Ti-Cr, and Ta-Zr-Cr are presented in Table II.

In our copending patent applications, Ser. No. 755,658 Wear Resistant Materials" and No. 755,662 Wear and Abrasion Resistant Materials we have described and claimed certain nitrided alloy systems consisting of vanadium and/or columbium and/or tantalum; titanium and/or zirconium, and molybdenum and/or tungsten. Said patent applications are assigned to the assignee of this application of their teachings are incorporated by reference herein. We now find that the compatibility of molybdenum or tungsten with chromium in such nitrided alloys is demonstrated and a number of such exam ples or nitrided quaternary alloys included herein are presented in Table II. It should be noted that the addition of chromium lowers the temperatures at which useful nitrided materials can be produced compared with the ternary alloys containing only molybdenum or tungsten. The excellent performance of Cb-20 Ti-15 Mo-lO Cr included within the scope of our invention is shown in Table III hereof.

Still another nitrided ternary alloy system included herein is that of columbium-titanium-rhenium. Useful materials are illustrated in Table II. Cb-25 Ti-20 Re nitrided at 3,250 F. for two hours showed a tool wear of 0.004 and 0.003 inch after cutting at 750 and SFM, respectively. Similarly, as is evident from Table II, useful nitrided materials were formed from the alloys Ta-25 Ti-15 Re, Cb-30 Zr-20 Re, and Cb-25 Ti-lO Mo-lO Re; such rhenium-containing materials exhibit even lower tool wear in cutting than do the chromium containing materials of this invention. Both such materials are included within the scope of our invention. The nitrided alloy Cb-70 Ti-lO Re does not pass our tests and is not included within the scope of our invention.

Manganese has been added as a ternary addition and as a quartemary addition in conjunction with molybdenum with good results. V-25 Ti-lO Mo-lO Mn cut well at 750 SFM and showed chipping around the Ra impressions when nitrided at 2,800 F. The V-25 Ti-lO Mn composition passed the cutting test when nitrided at 2,250 F. for 8 hours. Cb-3O Ti-lO Mn and Cb-25 Ti-lO Mo-IO Mn showed good performance after nitriding at 3,250 F. and 3,050 F., respectively. Such materials are included within the scope of our inventions.

A comparison of two representative materials falling within the scope of this invention with one of the best presently available sintered carbide materials is set forth in Table III:

TABLE III These alloys may be reacted E other nitriding environments like argon-2.5 percent nitrogen with similar weight pickup and hardening. Thus a variety of nitrogen containing environments can be used to produce similar hardened materials. However, upon reacting in argon0.l percent nitrogen under low gas flow conditions, the effect of lowered nitrogen availability is observed and a somewhat modified reaction product is obtained. Since our surface reacted composites are in a thermodynamically metastable condition, those skilled in the art will realize that a variety of heat treatments, including multiple and sequential treatments, can be used to modify the reaction structure and resulting properties whether performed as part the overall nitriding reaction or as separate treatments. We have also nitrided at higher temperatures (and times) that normally would produce some embrittlement and then subsequently annealed in inert gas as a tempering or drawing operation to improve toughness. This duplex treatment results in a deeper reaction product with the hardness-toughness relationship controlled by the tempering temperature and time.

The present useful alloys could be produced by powder processing techniques. Also such alloys could be employed on another metal or alloy as a surface coating or cladding and with the proper selection, a highly ductile or essentially unreacted substrate can be obtained. For example, columbium or tantalum are much less reactive to nitrogen when used in conjunction with the alloys and molybdenum is inert to nitrogen. The nitrided material can be used as a mechanically locked insert or it can be bonded or joined by brazing, for example, to a substrate.

We have also observed the excellent corrosion resistance of both the alloys and the nitrided alloys in strong acids, and these materials could effectively be employed for applications requiring both corrosion and abrasion resistance. Both the alloys and the nitrided alloys possess good structural strength. Thus, the materials can be employed for applications involving wear resistance and structural properties hardness, strength, stiffness, toughness) at room and elevated temperatures. Other useful properties of the nitrided materials include good electrical and thermal conductivity, high melting temperature, and thermal shock resistance.

Although the alloys receptive to nitriding can be produced by coating or surface alloying techniques, many uses involve the forming and machining of a homogeneous alloy. One of the advantages in utility of these materials is our ability to form the metallic alloys by cold or hot working and/or to machine (or hone) to shape in the relatively soft condition prior to final nitriding. Only minimal distortion occurs during nitriding and replication of the starting shape and surface finish is excellent. The final surface is reproducible and is controlled by original surface condition, alloy composition, and nitriding treatment. For some applications, the utility would be enhanced by lapping, polishing, or other finishing operations after nitriding. The nitrided surface is quite hard but only a small amount of material removal is required to produce a highly finished surface.

The materials containing minumum amounts of Group III elements such as chromium or rhenium pass our test and exhibit good wear resistance, but the preferred nitrided compositions exhibiting the lowest wear in our 750 SFM tests contain somewhat higher amounts of such additives. For example the performance of nitrided V-25 Ti-lO Cr at 750 SFM is superior to V-25 Ti-2 Cr. However, in adding increasing amounts of chromium, the unnitrided alloy is hardened and the formability is decreased. Thus an optimum alloy range exists having sufficient Group III elements (or optionally further additions of M or W to the ternary or more complex alloy) but with such additions limited to maintain good formability in the unnitrided alloys as shown in the following table.

Forging M. room temperature.

For a series of unnitrided Cb-Ti-Re alloys, similar hardening is observed and the Ra hardness of Cb-30 Ti-5 Re, Cb-25Ti- 20Re, and Cb-l5Ti-4ORe is 55, 69, and 75, respectively. The alloy Cb-25Ti-20 Re is malleable but shows reduced ductility compared to Cb-3OTi-5Re. The alloy Cb-25Ti-l0Mo-l0Re exhibited a hardness of Ra 67 and the malleability was similar to Cb-25Ti-2ORe. The Cb-l5Ti-40Re alloy fractured immediately upon cold forging and in addition showed a propensity to chip during machining; a sharp edge was difficult to prepare. Thus, alloys containing lower Group III (and Mo and/or W) and higher titanium content are more readily formed. Of course, the titanium content must be limited to 50 percent for retention of wear resistance in the nitrided materia1.

It should be noted that all percentages presented herein are by weight.

When one wishes to make use of the nitrided alloy systems of our invention certain compositional ratios and formulas must be employed in some cases to determine whether or not the material will be useful to meet the cutting test criteria established in this specification. These factors have been briefly noted before but now they should be considered in some detail to fully understand the teachings hereof. A modest mathematical statement is required. Such formulas represent linear proportionate amounts based upon weight percentages.

In the present specification and claims the following ratios ha l letqthet ewins. m il n s;

(that is, the concentration of columbium to total columbi- .B 1B! i? 2@ q 1 9i9mL5W???.

It should be noted that the concentration of columbium, tantalum, and/or vanadium may be as low as 30 percent in certain of the present systems to a maximum of percent. In certain systems the minimum tantalum content should be somewhat higher than 30 percent because of other compositional limitations.

The titanium and/or zirconium content ranges from a minimum of 5 percent to a maximum given by the formula 50A+50+35B.

The minimum chromium, manganese, rhenium, molybdenum and/or tungsten content is 2 percent except when the content of group II metals is greater than 42 percent in which case group III Mo W content must be greater than group ll minus 40.

The maximum amount of chromium, manganese, rhenium, molybdenum and/or tungsten in ternary or more complex alloys hereof is given by the following:

Where D equals the maximum chromium content when chromium is present alone of group III and molybdenum and/or tungsten are not present.

Where E equals the maximum rhenium content when rhenium is present alone of group III metals and molybdenum and/or tungsten are not present.

In higher alloyed systems the following compositional requirements must be met:

Maximum Cr =D-D (Mn/20 +Re/E +Mo/50 +W/50) Maximum Mn =20-20 (Cr/D +Re/E +Mo/50 +W/50) Maximum Re =E-E (Cr/D +Mn/20 +Mo/50 +W/50) Maximum Mo 50-410 (Cr/D +Mn/20 +Re/E +w/50) Maximum W =50-50 (Cr/D +Mn/20 +Re/E +Mo/50) We should next briefly illustrate the applicability of the foregoing relationships in determining whether or not it purticular nitrided alloy system has utility as set forth above and falls within the scope hereof.

As shown in Table II the nitrided alloy V-65 Ti-lO Cr falls without the scope hereof. The vanadium content (25 percent) is too low. But then consider the alloy 45 V-40 Ti-l5 Cr nitrided as herein taught.

In this case the vanadium content falls within the proper range. Titanium content is greater than the 5 percent minimum. Maximum titanium is given by the relationship 50A+50C+35B. In this case A or B= because of no columbium or tantalum being present. C=45/(45+0+0) =1 Thus, maximum titanium in such system is governed by (50 (0) +50 (1) +35 (0) )=50 weight percent. Thus the titanium content is acceptable.

The maximum chromium content is given by the relationship D =(45C+20A+1OB) Substituting:

D =(45 (1) +20 (0) +10 (0) =45 weight percent, maximum chromium accordingly, the alloy 45V-40 Ti l5 Crfalls within the scope hereof.

In addition to the nitrided alloy systems set forth above we have discovered that certain alloys, which are nitridable to form the foregoing useful materials illustrate considerable utility per se and are the preferred materials to use in practicing the nitrided aspects of our invention. Such alloys fall within the following compositional ranges:

More than 30 percent but less than 50 percent of titanium and/or zirconium, form to 25 percent chromium and/or rhenium, balance columbium, vanadium and/or tantalum. When tantalum is present the upper limit of titanium and/or zirconium is lower. In such alloy system one may optionally add from 5 to percent molybdenum and/or tungsten thereby replacing a like percentage of chromium and/or rheni- Within such range of alloy composition we find the following to be quite good:

a. more than 30 percent but less than 50 percent titanium and/or zirconium, form 10 to percent chromium, balance vanadium;

b. More than percent but less than 50 percent titanium and/or zirconium, 10 to 20 percent chromium, balance columbium with the optional addition of from 5 to 15 percent molybdenum and/or tungsten replacing a like percentage of chromium and wherein the minimum chromium content is at least 5 percent;

c. more than 30 percent but less than 50 percent titanium and/or zirconium, 10 to 25 percent rhenium, balance columbi- The excellent cutting properties and wear resistance of the nitrided materials can be effectively employed with the other useful properties of the alloys and nitrided materials to produce a wide range of products. Some of these are: single point cutting tools, multiple point cutting tools (including rotary burrs, files, routers and saws), drills, taps, punches, dies for extrusion, drawing, and of the forming operations, armor, gun barrel liners, impeller or fan blades, EDM (Electrical Discharge Machining) electrodes, spinnerets, guides (thread, wire, and other), knives, razor blades, scrapers, slitters, shear,, forming rolls, grinding media, pulverizing hammers and rolls, capstans, needles, gages (thread, plug, and ring), bearings and bushings, nozzles, cylinder liners, tire studs, pump parts, mechanical seals such as rotary seals and valve components, engine components, brake plates, screens feed screws, sprockets and chains, specialized electrical contacts, fluid protection tubes, crucibles molds and casting dies, and a variety of parts used in corrosion-abrasion environments in the papermaking or petrochemical industries, for example.

It will be understood that various modifications and variations may be affected without departing from the spirit or scope of the novel concepts of our invention.

We claim as our invention:

1. A nitrided material having a gradated multiphase structure containing nitrided metal extending essentially from the i surface inward which has excellent cutting and wear resistant properties consisting essentially of at least one metal selected from each of the groups I, ll and Ill.

Wherein group I consist of columbium, tantalum and vanadium group II consists of titanium and zirconium; group III consists of chromium, rhenium, and manganese.

With the optional alloying therein of a metal selected from the group consisting of molybdenum and tungsten and mixtures thereof; and wherein a. there is a minimum of 30 percent and a maximum of percent of one or more group I metals;

b. the content of group II ranges from 5 percent to a maximum of 50A+50C+35B.

c. there is a minimum of 2 percent of group III metals +No +W except when group ll metal content is greater than 42 percent in which case group III +Mo +W content is greater than group II content minus 40.

(1. maximum chromium =D-D (Mn/20+Re/E +Mo/5O +W/ e. maximum Nn =20-20 (Cr/D +Re/E +No/50 +W/50) f. maximum Re =E -E (Cr/D +Nn/20 +No/50 +W/50) n g. maximum No =50-50 (Cr/D +Mn/20 +Re/E +W/50) h. Maximum W =50-50 (Cr/D +Mn/20 +Re/E +Mo/50) and wherein D=(45C+20A +108) E=(20C+50A +508).

2. The material as defined in claim 1 wherein the nitrogen pickup thereof is at least 1 milligram per square centimeter of surface area, the surface microhardness is at least 1,000 diamond pyramid numerals and the reaction depth to which such hardness is developed is at least 0.5 mil.

3. The material as defined in claim 1 consisting essentially of from 30 to 85 percent vanadium, from 2 to 45 percent chromium, and from 5 to 50 percent titanium.

4. The material as defined in claim 1 consisting essentially of from 30 to 85 percent vandium, from 2 to 45 percent chromium, and from 5 to 50 percent zirconium.

5. The material as defined in claim 1 consisting essentially of from 30 to 85 percent columbium, from 2 to 20 percent chromium, and from 5 to 50 percent titanium.

6. The material as defined in Claim 1 consisting essentially of from 30 to 85 percent columbium, from 2 to 20 percent chromium, and from 5 to 50 percent zirconium.

7. The material as defined in claim 1 consisting essentially of from 30 to 85 percent columbium, from 2 to 50 percent rhenium and from 5 to 50 percent titanium.

8. The material as defined in claim 1 consisting essentially of from 30 to 85 percent tantalum, form 2 to 50 percent rhenium, and from 5 to 35 percent titanium.

9. The material as defined in claim 1 consisting essentially of:

a. from 5 to 50 percent titanium,

b. from 2 to 50 percent content of total rhenium plus a metal selected from the group consisting of tungsten and molybdenum and mixtures thereof wherein therein there is at least 2 percent rhenium; and

c. from 30 to 85 percent columbium.

10. The material as defined in claim 1 consisting essentially a. from 5 to 35 percent titanium,

b. from 2 to 50 percent content of total rhenium plus a metal selected from the group consisting of tungsten and molybdenum and mixtures thereof wherein therein there is at least 2 percent rhenium; and

c. from 30 to 85 percent tantalum.

11. The material as defined in claim 1 consisting essentially of:

a. from 5 to 50 percent titanium;

b. from 2 to 20 percent chromium;

c. wherein the total content of chromium plus a metal selected from the group consisting of molybdenum, tungsten and mixtures thereof ranges from 2 to 50 percent, and

d. from 30 to 85 percent columbium.

int...

12. The material as defined in claim 1 consisting essentially selected from the group consisting of molybdenum, tungf; sten and mixtures thereof ranges from 2 to 50 percent,

a. from 5 to 50 percent titanium; and

b, fro 2 t 45 r e t h i d. from 30 to 85 percent vanadium.

c. wherein the total content of chromium plus a metal 5 UNITED STATES PATENT AND TRADEMARK OFFICE CERTEFEQATE @F CRECTKN PATENT NO. 3,644,153 DATED February 22, 1972 Page 1 of 2 |NVENTOR(5) I John J, Rausch and Ray J. Van Thyne It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 43, "embodying" should read employing Column 3, line 54, "spilled" should read spalled Column 6, line 5, after "invention" insert V-5OZr-30Cr which is not included within the scope of our invention Column 6, line 54, after "showed" insert no Column 7, line 36, before "hardness" insert Column 8, line 48, before "+35B" insert C Column 8, line 61, the 2 equal signs within the parenthesis should read Column 9, line 28, "form" should read from Column 9, line 38, "form" should read from Column 10, line ll, "No" should read Mo Column 10, line 17, "Nn" should read Mn Column 10, line 17, "No" should read Mo UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF QQRRECTEON PATENT NO. I 3, 644, 153

DATED February 22, 1972 INVIENTOR(S) Page 2 of 2 John J. Rausch and Ray J. Van Thyne It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 10, line 18, "Nn" should read Mn and "No" should read Column 10, line 19 "No" should read Mo Column 10, line 37, "vandium" should read vanadium Signed and gcaled-thr's Twenty-second Day 0? March 1977 [SEAL] A lies I:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uflatenrs and Trademarks 

2. The material as defined in claim 1 wherein the nitrogen pickup thereof is at least 1 milligram per square centimeter of surface area, the surface microhardness is at least 1,000 diamond pyramid numerals and the reaction depth to which such hardness is developed is at least 0.5 mil.
 3. The material as defined in claim 1 consisting essentially of from 30 to 85 percent vanadium, from 2 to 45 percent chromium, and from 5 to 50 percent titanium.
 4. The material as defined in claim 1 consisting essentially of from 30 to 85 percent vandium, from 2 to 45 percent chromium, and from 5 to 50 percent zirconium.
 5. The material as defined in claim 1 consisting essentially of from 30 to 85 percent columbium, from 2 to 20 percent chromium, and from 5 to 50 percent titanium.
 6. The material as defined in Claim 1 consisting essentially of from 30 to 85 percent columbium, from 2 to 20 percent chromium, and from 5 to 50 percent zirconium.
 7. The material as defined in claim 1 consisting essentially of from 30 to 85 percent columbium, from 2 to 50 percent rhenium and from 5 to 50 percent titanium.
 8. The material as defined in claim 1 consisting essentially of from 30 to 85 percent tantalum, form 2 to 50 percent rhenium, and from 5 to 35 percent titanium.
 9. The material as defined in claim 1 consisting essentially of: a. from 5 to 50 percent titanium, b. from 2 to 50 percent content of total rhenium plus a metal selected from the group consisting of tungsten and molybdenum and mixtures thereof wherein therein there is at least 2 percent rhenium; and c. from 30 to 85 percent columbium.
 10. The material as defined in claim 1 consisting essentially of: a. from 5 to 35 percent titanium, b. from 2 to 50 percent content of tOtal rhenium plus a metal selected from the group consisting of tungsten and molybdenum and mixtures thereof wherein therein there is at least 2 percent rhenium; and c. from 30 to 85 percent tantalum.
 11. The material as defined in claim 1 consisting essentially of: a. from 5 to 50 percent titanium; b. from 2 to 20 percent chromium; c. wherein the total content of chromium plus a metal selected from the group consisting of molybdenum, tungsten and mixtures thereof ranges from 2 to 50 percent, and d. from 30 to 85 percent columbium.
 12. The material as defined in claim 1 consisting essentially of: a. from 5 to 50 percent titanium; b. from 2 to 45 percent chromium; c. wherein the total content of chromium plus a metal selected from the group consisting of molybdenum, tungsten and mixtures thereof ranges from 2 to 50 percent, and d. from 30 to 85 percent vanadium. 